The basic concept of a hair roller is a central drum or cylinder on which the hair is wrapped into a curl and retained by means of a secondary member comprising an elastic band or some type of pivotal strap or bar, in either instance the secondary member frictionally engaging the hair against the roller body.
Typically the device is of the type using an elastic band havine one end which rotates so that the elastic band may be engaged in the rotating end to basically secure the hair on the roller, and then the rotatable end can be adjusted slightly to increase the tension on the band. However, when it does this, the hair which is already rolled on the central drum is displaced either more tightly or more loosely around the drum, so that the tightening function automatically also affects the tightness of the hair roll, which is not desirable.
It is also true of most conventional rollers that it is not possible to entirely remove the band structure from the roller drum in order to provide maximum agility and flexibility of rolling the hair.